If Firms in a Monopolistically Competitive Industry Are Making an Economic

If firms in a monopolistically competitive industry are making an economic profit, then definitely there is

A) a leftward shift in each firm's demand curve as new firms enter the market.
B) a rightward shift in each firm's marginal revenue curve as new firms enter the market.
C) an upward shift in each firm's cost curves as new firms enter the market.
D) All of the above answers are correct.